Re: Weird distorted shapes

The problem looks more apparent in this other picture... See how the
'straight' lines have a curve to them...

https://www.dropbox.com/s/i1r76l4dif9vv2w/2014-03-02%2020.10.19.jpg

----- Original Message -----
From: "Clay Cowgill" <c.cowgill@comcast.net>
To: <vectorlist@vectorlist.org>
Sent: Tuesday, March 04, 2014 6:46 PM
Subject: RE: VECTOR: Weird distorted shapes

> >Look at this screen shot of another builders results...
>>https://www.dropbox.com/s/owa3vq5l6f0lgv2/100_3343_zps3521fb63.jpg
>>
>>Notice the blue is perfectly formed, but the green is all messed up
>
> That looks to me as though the green channel amp is slow to turn on. The
> vectors look pretty straight-- they're just either 'fading in' (or 'fading
> out' depending on the direction of the draw I suppose) before reaching the
> end of the line. Could be a tube issue as well. Looking at the green
> color
> output vs. a deflection channel (or two) would probably show the problem
> on
> a scope.
>
> There might be a little high frequency 'jitter' in there somewhere that's
> causing the hash on some of the green verticals. Hard to tell with a
> picture-- really need video there. Also could just be that the shadow
> mask/dot pitch on the tube is pretty big and sometimes the green verticals
> are straddling the mask and appearing on one side or the other.
>
> For Joel's original problem, I would probably try to trace things through
> the deflection section with the scope-- put the Star Wars boardset X
> output
> on one channel and then follow X through the deflection section with the
> other channel. Set the volts/div to try to keep the waveforms about the
> same vertical size on the scope and compare them visually. You should be
> able to see that amount of difference/distortion on the screen so you
> should
> be able to see when it appears in the deflection board. (Hard to debug
> without knowing the design, but I'm assuming there's probably some sort of
> pre-amp that you could look at before it gets to a power-amp stage.)
>
> It does kinda look like its more prominent on short vectors which is
> probably a clue. To be more useful I'd want to see the schematic for the
> deflection section and/or the layout. Curvey/distorted things like that
> could be related to opamp speeds or outputs getting too close to the rails
> or L/C or maybe power...
>
> -Clay
>
>
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Received on Tue Mar 4 15:07:48 2014